Power boating has become an increasingly popular past time around the world. In addition to recreational use of power boats, power boats are also utilized in commercial and military settings. Generally, the use of the boat determines the type of hull which will be utilized in constructing the boat. For example, many people who operate power boats for recreation require increased speed for sports such as water skiing, while also requiring stability for safety. In addition, many recreational consumers require cabins for comfort and want fuel efficiency for economic and environmental reasons. In contrast, commercial boats may require less speed, but more stability for their particular application, and fuel efficiency remains a concern. Conventional hull shapes for mono-hull boats can be generally characterized as displacement type hulls, semi-displacement type hulls and planing hulls.
Displacement hulls utilized in power boats are well known in the art. Such hulls have a shape which is not overly sensitive to weight, but which does not exhibit any lift characteristics. Lift is the force that enables a hull to raise up out of the water as the forward thrust provided by the engine and propeller increase, thereby increasing the boat's speed as wetted surface is decreased. Thus, while displacement type hulls afford the operator with seaworthy characteristics, top speeds of these vessels are generally governed by waterline length. The maximum speed of displacement hulls has been conventionally accepted to be limited to the theoretical hull speed formula computed by multiplying the square root of the length of the hull's waterline (WL) by 1.4, i.e. maximum speed=1.4√{square root over (W)}L.) For example, a boat with a 30 foot waterline should have a theoretical maximum hull speed of about 7 knots. Beyond their theoretical optimal speed conventional displacement hulls begin to sink into the water, rather than lift out of the water, thereby decreasing their speed. Thus, increasing horsepower does not equate in such hulls to an increased speed, but rather can lead to the hull being driven lower into the water and increasing the wetted surface, reducing speed to a point that the vessel can actually sink. Generally, displacement type hulls are utilized for long range power boats, where weight carrying and fuel tankage capabilities for providing range outweigh the need for increased speed. In addition, due to their round shaped hull sections, displacement powerboats tend to have a rolling motion in a seaway and generally require some method of roll dampening, typically by using paravanes or gryro controlled underwater fins. Even displacement vessels as large as 600 foot passenger cruise ships use roll dampening devices for passenger comfort.
Another style hull which is utilized in power boats, such as lobster boats, is a semi-displacement hull. Semi-displacement hulls partially lift out of the water as forward propulsion is increased, but at the same time the wave created by the bow is increased creating drag as speed and power are increased. Semi-displacement hulls have advantages for use as fishing boats and commercial craft as their speed can be adjusted based on the load carried by the boat. Motion in a seaway for semi-displacement hulls is generally better than displacement hulls due to their flat aft sections. However, offshore fishing vessels still utilize paravanes on the outriggers for dampening rolling action to allow the crew to operate safely. Semi-displacement hulls are normally not as fast as planing hulls, but are faster than displacement hulls. Conventionally powered and loaded semi-displacement hulls normally operate at 2.0 to 2.3 times the square root of the waterline length. However, because of the bow wave factor and the drag created by their very flat (almost horizontal deadrise) aft sections of the hull, such semi-displacement hulls require a significant amount of power to operate at higher speeds, regardless of load. For example, a 35 foot semi-displacement hull boat having a single, 350 hp engine would typically burn about 20 gals. per hour at a maximum speed of about 14 knots.
Planing hulls generate lift as forward propulsion is increased, reducing the amount of hull which is in the water and dramatically increasing speed as compared to displacement type hulls. Most currently available power boats utilized deep V-shaped hulls or moderate deep vee shapes. While the speed of such boats is good, they require large amounts of horsepower and, consequently, burn a considerable amount of fuel in order to get the hull out of the water to attain the faster speeds. For example, a 40 foot deep V hull boat having twin 350 hp engines would typically burn about 40–50 gals. per hour at a maximum speed of about 25 knots. In addition, a planing hull is very sensitive to allowable weight, limiting the amount of fuel that can be carried, thus limiting range of operation. Speeds in excess of 80 knots have been achieved in planing hulls using enormous power plants with significant fuel burn. Approx. 80% of the pleasure power boats in the United States use planing hulls because of their speed and comfortable motion in flat and moderate seas. However, maintaining minimum planing speeds, usually in excess of 12 to 14 knots, in high sea conditions can be very uncomfortable due to the pounding motion created by the flat hull sections. Using a planing hull at speeds below planing speed can also be uncomfortable due to the hull shape which obtains it's stability from water moving fast across the underwater sections of the hull.
Improvements to all hull types are continually being made in an effort to optimize specific hull characteristics, according to the particular use of the boat. However, to date no hull design has been developed for power boats which has successfully exhibited good fuel economy and range at variable operating speeds while also providing a stable, comfortable ride.
Accordingly, there is needed in the art a power boat having a hull design which exhibits good to excellent fuel economy and range at variable operating speeds, while also providing a stable, comfortable ride.